docs: def process_response(self, request, response):
          """
          Update the storage backend (i.e., save the messages).
  
          Raise ValueError if not all messages could be stored and DEBUG is True.
          """
          # A higher middleware layer may return a request which does not contain
          # messages storage, so make no assumption that it will be there.
          if hasattr(request, '_messages'):
              unstored_messages = request._messages.update(response)
              if unstored_messages and settings.DEBUG:  # pragma: no-cover
                  raise ValueError('Not all temporary messages could be stored.')
          if hasattr(request, '_alarms'):
              unstored_alarms = request._alarms.update(response)
              if unstored_alarms and settings.DEBUG:  # pragma: no-cover
                  raise ValueError('Not all temporary alarms could be stored.')
          return response